1. Technical Field
The present invention relates to the technical field of devices for reading/authenticating banknotes. The invention also concerns handheld devices, particularly those which may be used by visually impaired persons, to identify different banknote denominations.
2. Discussion of Background Information
Optical properties of specific marking on currencies, or of the paper itself, are often used for discouraging forgery. For example, it is well known that high-quality non-fluorescent paper (not commonly available to the general public) is used for many currencies. This feature allows simply detecting forgery obtained by photocopying a banknote using conventional photocopier paper, as said paper fluoresces under UV light illumination due to the presence of optical brightner agent (which absorbs UV light to emit light at a higher wavelength in the visible region). Many other types of marking are known in the art: for example, luminescent ink or pattern printed on the banknote, a strip or a (possibly luminescent) security thread, marking with IR absorbing ink etc.
Other illustrative and non-limiting examples are the Canadian currency, which includes random points having bright secondary emission when exposed to UV light, or the Peruvian currency, which too has specific small features having bright secondary emission when exposed to UV light.
Banknote validators are of common use for scanning a banknote and determining its denomination and/or authenticating it, as illustrated, for example, with the banknote validators disclosed in the following U.S. Pat. No. 5,640,463, U.S. Pat. No. 5,960,103, U.S. Pat. No. 7,378,665 B2, U.S. Pat. No. 7,550,736 B2 and EP 1 471 472 B1, or the patent application GB 2 355 522 A.
Typically, these banknote validators use reflectance and/or transmittance properties of the banknotes relating to certain currencies, under illumination by appropriate light (for example, UV, white or IR light), to determine a denomination or check authenticity by comparing intensities, intensity thresholds, or intensity ratios, of light reflected and/or transmitted by said banknotes with some corresponding reference values for authentic banknotes.
Some banknotes validators can further detect the presence of fluorescent and/or phosphorescent material (i.e. luminescent material) on or within the banknotes, or even measure the corresponding luminescence intensity.
However, using reflectance or transmittance intensities, or luminescence intensity, necessitates having separate intense pulsed light sources (such as high-intensity emitting diodes), and adapted lenses to focalize reflected/transmitted light and obtain measurement data with a good signal/noise ratio. This makes miniaturization of the scanning head of a validator more difficult and increases its cost, particularly in case of a handheld validator. Moreover, using mere reflectance or transmittance intensities, cannot always allow discriminating certain denominations or discriminating counterfeit banknote. For example, for genuine US currency reflecting a high level of UV light without overall fluorescence, it is not possible to discriminate a counterfeit currency having these characteristics.
Some banknote validators, for better discriminating various denominations, use imaging of a specific marking of a banknote, or detection of marking with magnetic ink or conductivity properties, at a given place on the banknote (for example, a specific pattern printed on the banknote, a strip or a security thread, or a portion free of printed matter). However, as the position of the marking generally changes between denominations and series, these validators necessitates using a further means for distinguishing width from length and transporting the banknotes along a path through a banknote passageway, which includes control means and sensors for measuring a position of the banknote in said passageway during a scanning operation, so as to correctly find and detect properties of the marking. This is even more complex in case said checking must be performed whatever is an insertion sense and/or side of the banknote in the passageway. Besides being detrimental to miniaturization of the scanning head of the validator, this further means for transporting the banknote is not appropriate for a handheld equipment to be used by users (like visually impaired persons, for example). Indeed, said users would prefer inserting the banknote and simply passing it through the validator for scanning operation, while still holding the banknote.
Thus, there is clearly a need for a robust banknote validator capable to fully discriminate the denominations of a currency and reliably authenticate these denominations, which could even be a handheld device. Particularly, there is a need for such an handheld banknote validator adapted to visually impaired persons, as it is clear from a recently published report of ARINC Engineering services, LLC, for the Bureau of Engraving and Printing (BEP), which is a bureau within the United States Department of Treasury (Final Report, “Study to Address Options for Enabling the Blind and Visually Impaired Community to Denominate US Currency, contract S08-00156, July 2009).